Implementation plan

1. Probe current public metadata, classification filters, sample grids, and reservation pages. Record endpoint failures and current hosts.
2. Move shared Pydantic models and the async adapter into providers.usedirect. Keep thin concrete provider classes, using explicit URL configuration and booking-method overrides.
3. Add stable provider rows and a seed-only migration. Derive CLI choices/help from the registry so the metadata CLI can ingest every supported provider.
4. Verify date clipping, provider-specific request URLs and errors, per-instance caches, location defaults, atomic catalog/search refreshes, seed rollback, booking routes, and ingestion fan-out with synthetic tests.
5. Run Task quality gates and pre-commit, verify migration round trips in an isolated SQLite database, and update the roadmap/checklist and provider documentation.

Constitution check

• Shared backend logic stays independent from the synchronous legacy CLI.
• Async I/O, DTO interfaces, Task workflows, and strict typing follow the existing architecture.
• Shared behavior is extracted once; concrete implementations contain only real provider differences.
• Specifications precede implementation; API probes and synthetic regressions verify assumptions.